1. Field of the Invention
The present invention relates to a cryopump system, a cryogenic system, and an apparatus and a method of controlling a compressor unit.
2. Description of the Related Art
A cryogenic system comprising a cryogenic refrigerator and a compressor unit operative to supply refrigerant gas (operating gas) to the refrigerator is known. A system comprising a cryogenic apparatus (e.g., a cryopump) that utilizes a cryogenic refrigerator as a cooling source is also known as an example of a cryogenic system. In a cryogenic system, a compressor unit is sometimes controlled so that a differential pressure of refrigerant gas between a high pressure side and a low pressure side of a refrigerator is in agreement with a defined value. Such differential pressure stabilization control of a compressor unit contributes to reduction of power consumption of a system.